![]() Shorter wavelengths, like 207–222 nm (sometimes called “far UVC”) are believed to damage the proteins on the surface of the virus that it needs to attach to human cells. The 254 nm light damages the viral deoxyribonucleic acid (DNA) or ribonucleic acid (RNA) so that the virus cannot reproduce. Experts believe that different wavelengths disable viruses in different ways. However, 254 nm may not be the optimal wavelength for killing all viruses. To make a UV lamp, the glass is replaced with a material transparent to UV light, such as fused quartz. But the phosphor deposited on the glass surface of the bulb absorbs that light and re-emits it at longer wavelengths that humans can see. A fluorescent bulb actually produces UV light inside the bulb. These lamps are easy and cheap to manufacture because they use essentially the same technology as a fluorescent light bulb. By far the most common wavelength for germicidal light is 254 nm, produced by low-pressure mercury lamps. Two of the major design choices are the wavelength of light and the method of delivery. ![]() Some systems consist of just a bare lightbulb and a timer, while others are mobile robots that can reach hard-to-access places. Īt present there are many different designs for UV disinfection systems. cm −2 of 254 nm light will kill at least 99.99% of “any pathogenic microorganism”.According to the International Ultraviolet Association, it is generally accepted that a dose of 40 mJ Therefore, UVC light is just as novel to SARS-CoV-2 as the virus is to humans. UVA and UVB light rays have limited germ-killing ability because viruses and bacteria have had millions of years to adapt to them.īut UVC light (200–280 nm) is completely absorbed by our atmosphere and never reaches the surface of the earth. ![]() These are the rays that can cause sunburn if one stays outside too long without protection. The longest wavelengths are UVA (315–400 nm) and UVB (280–315 nm), which are found in ordinary sunlight. All of them are invisible to the human eye. UV light is generally divided into three classes, based on the wavelength of the light. Credit: Dimer UVC Innovations, with permission. It requires an operator, who is protected by a UV light shield, to push it. The GermFalcon is a UV disinfection device that can be wheeled up and down an airplane aisle. ![]()
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